WO2009149845A1

WO2009149845A1 - Foamed polyesters and methods for their production

Info

Publication number: WO2009149845A1
Application number: PCT/EP2009/003911
Authority: WO
Inventors: Heinrich Rüger; Michael Gisler; Linus Villiger; Cédric MÜNGER
Original assignee: Alcan Technology & Management Ltd.
Priority date: 2008-06-12
Filing date: 2009-06-02
Publication date: 2009-12-17
Also published as: CA2727639A1; CN102056967A; ES2439713T3; BRPI0915376A2; US20110082227A1; PL2288643T3; CA2727639C; EP2288643A1; DK2288643T3; KR20110036037A; JP5670321B2; PT2288643E; RU2482138C2; RU2011100164A; CN102056967B; EP2288643B1; JP2011522932A

Abstract

Foams composed of thermoplastic polyesters with high homogeneity, low open-cell factor and high elongation at break under shear stress, where the polyester foam comprises amounts of, for example, from 0.5 to 15% by weight of at least one thermoplastic elastomer, for example a thermoplastic copolyester elastomer, based on the weight of the foam. The foams are obtainable via foaming of a starting polyester of low intrinsic viscosity in a mixture with a modifier in the form of a premix comprising dianhydrides of tetracarboxylic acids and thermoplastic copolyester elastomers.

Description

Foamed polyesters and process for their preparation

The invention relates to foam bodies of thermoplastic polyesters, with high homogeneity, low open-cell content and high shear fracture elongation, containing as modifier dianhydrides of tetracarboxylic acids, means for producing the foamed bodies and processes for producing foamed polyesters.

For example, WO 93/12164 discloses foamed cellular polyesters and a process for their preparation. It is described that thermoplastic polyesters suitable for extrusion foaming have, for example, an intrinsic viscosity of more than 0.8 dl / g. In order to obtain the specified intrinsic viscosity value, a two-stage process is described, according to which a polyester having an intrinsic viscosity higher than 0.52 dl / g is added with a dianhydride of an organic tetracarboxylic acid and reacted to form a polyester having an intrinsic viscosity of 0.85 to 1.95 dl / g. Thereafter, the foaming process by extrusion foaming can be initiated with the thus prepared polyester. In some cases, further dianhydride can be added to an organic tetracarboxylic acid during extrusion foaming.

The disadvantage of this process is that two complex process steps are necessary in order to first mix the entire volume of polyester with the dianhydride of the tetracarboxylic acid and then bring it to reaction temperature in a solid phase reactor and several hours until the end of the reaction to keep. Only then does the actual foaming process follow.

According to US 5,288,764, foamed polyester can be obtained by forming a molten mixture and extruding this mixture. The mixture is made up of a major portion of polyester and a smaller portion of one Mixture of polyester with a substance formed, the chain extension, resp. Branch, causes.

The invention has for its object to propose foams made of polyester, means for their preparation and a process for their preparation in order to foam, resp. Foam bodies to arrive from thermoplastic polyesters with advantageous properties. Particularly sought-after foams of polyester have, for example, low density, high homogeneity, low open-celledness, high strength and, in particular, high shear fracture elongation. The foaming of polyesters to foam bodies is difficult to control process. In particular, intrinsically viscous polyesters (IV) can either not be foamed at all or, if foaming is still possible, the foams have poor properties, such as varying high density, high open-celledness, irregular pore distribution and low shear fracture elongation.

To solve this problem according to the invention, the polyester foam of the foam body contains at least one thermoplastic elastomer.

For example, foamed bodies of polyesters according to the invention contain thermoplastic elastomers in amounts of from 0.5 to 15.0% by weight, based on the weight of the foam body. Suitably amounts of thermoplastic elastomers from 0.5 to 12 wt .-%, and preferably from 1, 5 to 12% by weight, each based on the weight of the foam body.

The foam bodies of polyesters according to the present invention advantageously comprise as thermoplastic elastomers polymer blends or thermoplastic copolyester elastomers.

Thermoplastic elastomers consist of or contain polymers or a polymer blend (blend) which exhibits properties at service temperature. similar to vulcanized rubber, but which can be processed and worked up at elevated temperatures like a thermoplastic. The polymer blends have a polymer matrix of hard thermoplastic with incorporated particles of soft crosslinked or uncrosslinked elastomers. The thermoplastic copolyester elastomers contain hard thermoplastic sequences and soft elastomeric sequences. The thermoplastic copolyester elastomers contain polyester blocks, expediently from a diol, preferably from 1,4-butanediol or 1,2-ethanediol, and a dicarboxylic acid, preferably terephthalic acid, which are reacted with polyesters which carry hydroxyl end groups in a condensation reaction - were restert.

Thermoplastic elastomers (for example according to prEN ISO 18064) are also known under the abbreviation TPE and the subgroups TPO (thermoplastic olefin elastomers), TPS (thermoplastic styrene elastomers), TPV (thermoplastic rubber vulcanizates), TPU (thermoplastic urethane elastomers), TPA (thermoplastic polyamide elastomers), TPC (thermoplastic copolyester elastomers) and TPZ (other unclassified thermoplastic elastomers) known. The TPEs include block or segmented polymers such as thermoplastic styrenic block polymers, thermoplastic copolyesters, polyetheresters, thermoplastic polyurethanes or polyether-polyamide block copolymers. The TPEs obtain their elastomeric properties either by copolymerizing hard and soft blocks or blending a thermoplastic matrix. In the case of graft copolymerization, the hard segments form so-called domains, which function as physical crosslinks. TPE are repeatedly melted and processed. The TPE, described as thermoplastic copolyester elastomers, resp. also called TPC, are divided into the TPC-EE with soft segments with ether and ester linkages and the TPC-ES / -ET with soft polyester segments, respectively. Polyether. In the present case, the TPC-EE are of particular interest. The thermoplastic copolyester elastomers, resp. thermoplastic copolyester or thermoplastic polyetherester, resp. elastomeric copolyether restoratives are alternately composed of hard polyester segments and soft polyether segments. Depending on the type and length of the hard and soft segments, a wide hardness range is adjustable. Thermoplastic copolyesters are block copolymers consisting on the one hand of amorphous soft segments of polyalkylene ether diols and / or long-chain aliphatic dicarboxylic acid esters and on the other hand of hard segments of crystalline polybutylene terephthalate. The preparation of the elastomeric copolyether esters takes place in the melt by transesterification reactions between a terephthalate ester, a polyalkylene ether glycol (eg polytetramethylene ether glycol, polyethylene oxide glycol or polypropylene oxide glycol) and a short-chain diol, for example 1,4-butanediol or 1,2-ethanediol.

In order to increase the molecular weight of polyesters, a modifier can be added to the polyester. The modifier is, for example, a dianhydride of an organic tetracarboxylic acid (tetracarboxylic acid dianhydride). Preferred dianhydrides are the dianhydrides of the following tetracarboxylic acids:

Benzene-1, 2,4,5-tetracarboxylic acid (pyromellitic acid), 3,3 ', 4,4'-diphenyltetracarboxylic acid, 3,3', 4,4'-benzophenonetetracarboxylic acid, 2,2-bis- (3,4-) dicarboxyphenyl) -propane, bis (3,4-dicarboxyphenyl) ether, bis (3,4-dicarboxylphenyl) thioether, naphthalene-2,3,6,7-tetracarboxylic acid, bis (3,4-dicarboxylphenyl) sulfone, tetrahydrofuran-2,3,4,5-tetracarboxylic acid, 2,2-bis (3,4-dicarboxlphenyl) hexafluoropropane, 1, 2,5,6-naphthalenetetracarboxylic acid, bis (3,4-dicarboxyphenyl) - sulfoxide and mixtures thereof. The preferred dianhydride is pyromellitic dianhydride (benzo! -1, 2,4,5-tetracarboxylic acid 1, 2: 4,5-dianhydride).

Starting materials which can be used to produce foamed polyesters are polyesters, such as thermoplastic polyesters obtainable by polycondensation of aromatic dicarboxylic acids with diols. Examples of aromatic acids are terephthalic and isophthalic acids, naphthalene dicarboxylic acids and diphenyl ether dicarboxylic acids. Examples of diols are glycols such as ethylene glycol, tetraethylene glycol, cyclohexanedimethanol, 1,4-butanediol and 1,2-ethanediol.

Polyesters of or containing polyethylene terephthalate, polybutylene terephthalate and polyethylene terephthalate copolymers containing up to 20% of isophthalic acid are preferred.

A particularly important feature of the polyesters used as starting material, which are modified according to the invention and foamed to form the foam bodies according to the invention, is the intrinsic viscosity. It has not been possible to produce foams starting from polyesters having an intrinsic viscosity of about 0.4 dl / g. According to the present invention, starting materials, such as of polyesters having an intrinsic viscosity as low as about 0.4 dl / g and above, and especially of polyesters having an intrinsic viscosity of, for example, 0.6 to 0.7 dl / g and above, can reliably form foams be manufactured with the required properties. In order to increase low intrinsic viscosities, the proportion of modifier, in particular the tetracarboxylic dianhydride, based on the polyester used, must be increased accordingly. By choosing the concentration of modifier in the masterbatch and the amount of masterbatch used with respect to the amount of polyester, the intrinsic viscosity of the processed polyester, and hence its foamability, is easily controlled. For example, the intrinsic viscosity of 0.6 to 0.7 dl / g can be increased by the modification to above 1, 0 or even 1, 2 dl / g and above. The present invention also relates to compositions for producing foam bodies from polyesters of high homogeneity, low open-cell content and high shear fracture strain, containing as modifier dianhydrides of tetracarboxylic acids. The compositions are a masterbatch containing thermoplastic elastomers, such as copolyester thermoplastic elastomers, in amounts of from 25 to 95% by weight, based on the weight of the composition, and dianhydrides of tetracarboxylic acids in amounts of from 5 to 30% by weight, based on the weight of the agent.

Preference is given to compositions for producing foam bodies from polyesters, where the composition is a masterbatch comprising thermoplastic copolyester elastomers in amounts of from 25 to 95% by weight and dianhydrides of a tetracarboxylic acid in amounts of from 5 to 30% by weight and 0 to 70%, preferably 1 to 50 wt .-%, each based on the weight of the composition, stabilizers, nucleating agents, flame retardants and / or polyester, suitably a polyester of the same quality, such as a starting polyester to be modified.

The means, i. the premix can be prefabricated and stored temporarily on a case-by-case basis. Thereafter, in the quantities provided, the premix and the polyesters to be foamed can be mixed together. This mixture of premix and polyesters can be further fed to the foaming process and processed into foam bodies.

The present invention also relates to a process for the preparation of foam bodies of polyesters of high homogeneity and shear rate elongation, containing as modifying agent dianhydrides of a tetracarboxylic acid.

According to the novel process for producing the foam bodies, a polyester resin is admixed with a premix of thermoplastic elastomers, such as thermoplastic copolyester elastomers, and dianhydrides of a tetracarboxylic acid, to give a foam body, containing the ther- moplastic copolyester elastomers in amounts of 0.5 to 15 wt .-%, based on the weight of the foam body, foamed.

The premix of thermoplastic elastomers such as thermoplastic co-polyester elastomers and dianhydrides of a tetracarboxylic acid is prepared as a precursor by mixing the ingredients. The masterbatch may contain from 25 to 95% by weight, based on the premix, copolyester elastomers and from 5 to 30% by weight, based on the masterbatch, of tetracarboxylic dianhydride. Suitably, the premix contains 50 to 90 wt .-%, preferably 80 to 90 wt .-%, based on the masterbatch, copolyester elastomers and 10 to 25 wt%, preferably 10 to 15 wt .-%, based on the premix, tetracarboxylic dianhydride ,

The premix may contain as further constituents, for example a total of 0 to 70%, preferably 0.1 to 70% by weight and in particular 1 to 50% by weight, for example polyesters, stabilizers, nucleating agents, fillers and flame retardants. The polyesters listed on the other components may be of the same quality as the polyesters to be modified, i. Starting polyester, e.g. with an intrinsic viscosity above about 0.4 dl / g and in particular polyester having an intrinsic viscosity of about 0.6 to 0.7 dl / g and above, be.

The preparation of the premix can be carried out by feeding the components into a mixer, for example a screw extruder, such as a single- or twin-screw extruder or a multi-screw extruder etc., and intimately mixing the components over a period of 10 to 120 seconds at temperatures of 200 to 260 ⁰ C take place. The premix can be discharged from the mixer and be granulated in a further processable form, for example.

To produce the foam body of polyesters is carried out by a mixing and foaming process. For example, a polyester with a - Intrinsic viscosity of at least 0.4 dl / g, submitted and mixed with the premix. The premix can be used in amounts of 1, 0 to 20.0 wt .-%, based on the polyester. Advantageously, amounts of 2.0 to 4.0 wt .-%, based on the polyester.

In some cases, additional components can be added to the mixing and foaming process, in addition to the polyester and the premix. These are the stabilizers, fillers and flame retardants already mentioned, which can be added instead of or not already contained in the premix. The amounts of further components are, for example, up to 15% by weight, advantageously from 0.1 to 15% by weight, based on the sum of polyester and premix. Other components, for example for controlling cell size and cell distribution in the foam, can also be added to the mixing and foaming process. These are, for example, up to 5% by weight, suitably from 0.1 to 5% by weight, based on the sum of polyester and premix, of metal compounds of I. to III. Group in the periodic system, e.g. Sodium carbonate, calcium carbonate, aluminum or magnesium stearate, aluminum or magnesium myristate or sodium terephthalate and the other suitable compounds, such. Talc or titanium dioxide.

The components can be fed to and mixed in a reactor or mixer, for example a single- or twin-screw extruder or a multi-screw extruder or a tandem unit consisting of two single-screw extruders combined together or combined with one another, a twin-screw extruder and a single-screw extruder. The residence time of the components in the reactor or mixer can be for example from 8 to 40 minutes. The temperature during the residence time can be from 240 to 320 ^° C.

The blowing agent for foaming is also fed to the reactor or mixer, for example the extruders mentioned. Suitable propellants are, for example, easily vaporizable liquids, thermally decomposing substances that release gases or inert gases and mixtures or combinations mentioned Medium. The readily volatile liquids include saturated aliphatic or cycloaliphatic hydrocarbons, aromatic hydrocarbons and halogenated hydrocarbons. Examples are butane, pentane, hexane, cyclohexane, ethanol, acetone and HFC 152a. As an inert gas CO ₂ and nitrogen can be mentioned. The blowing agent is usually fed into the extruder after the feed zone, the components.

At the forming outlet opening of the extruder is continuously formed the foam body of substantially largely closed-cell foam, which may have, for example, a round, rounded, rectangular or polygonal cross-section. The foam body can then be as far as required, according to the use, deformed, cut and / or joined. If foamed bodies are produced, then the foamed bodies can be stacked next to one another and / or one above the other and processed to form foam blocks, in particular homogeneous foam blocks, with mutual release-resistant connection, such as mutual bonding or, in particular, welding. The foam bodies can be plate-shaped and stacked. The touching surfaces can be connected to each other over the entire surface, as if welded. This results in foam blocks with welds that run in the extrusion direction. It can, in particular transversely to the extrusion direction, resp. transverse to the welds, individual foam sheets are separated from the foam block.

The foamed body according to the invention has in particular the following advantageous features:

- Sort purity, there are only polyester and no other dissimilar polymers.

- Regular closed-cell pores.

The foam body according to the invention has, in particular, the following advantageous features at a bulk density of about 120 kg / m ³ :

Shear strength according to ISO 1922, for example greater than 1.0 N / mm ² , - shear modulus (G-modulus) according to ASTM C393, for example greater than 20 N / mm ² .

- Shear elongation at break according to ISO 1922, for example with values of more than 12%, suitably more than 16% and preferably more than 50%. - Compressive strength according to ISO 844, for example greater than 1.7 N / mm ²

- Pressure module (modulus of elasticity) according to DIN 53421, for example of greater than 90 N / mm ² .

- Open cell according to Airex method AM-19 according to ASTM D1056-07, for example, of less than 8% and in particular less than 4%. The open-cell measurement according to the Airex method AM-19 is carried out as described in ASTM D 1056, but calculated using a different formula: ASTM D 1059: W = [(AB) / B] × 100 with W = change in mass %]; A = final mass of specimen; and B = initial mass of specimen. Airex AM-19: OZ = [(AB) / (LxBxD)] x 100 where OZ = open cell [vol%] A = weight of sample after conditioning [g]; B = weight of the sample before conditioning [g]; L, B, D = length, width, thickness of sample [cm]; the density of water at 1 g / cm ³ is not explicitly indicated in the formula. According to the present invention, for example, values in the water adsorption test of less than 40% by weight, expediently less than 35% by weight and in particular less than 30% by weight are achieved.

The viscosity number of the resulting foam is determined according to ISO 1628/5 and may for example be more than 150 ml / g, approximately corresponding to an intrinsic viscosity of more than 1.2 dl / g. Preferably, a viscosity number of the resulting foam, determined according to ISO 1628/5, of, for example, more than 160 ml / g, approximately corresponding to an intrinsic viscosity of more than 1.30 dl / g.

The process according to the invention is also distinguished, for example, by the fact that no gel formation takes place during extrusion. The premix is fully miscible with the polyester and no second undesirable phase forms. The premix can be produced in devices known per se, the so-called compounding devices, the process being light is controllable. The properties of the resulting foam body can also be controlled in a simple manner by the choice of the thermoplastic copolyester elastomer (TPC) and the soft elastomers and hard thermoplastic sequences contained therein.

Examples:

Premix Example 1:

Thermoplastic copolyester elastomer (TPC) in the form of granules with a Shore hardness of 55 D is dried for 4 hrs. At 100 ⁰ C by means of hot air. On a co-rotating twin-screw extruder with 27 mm cylinder diameter and an L / D ratio of 40, 85 wt .-% TPC and 15 wt .-% pyromellitic dianhydride (PMDA) at a cylinder temperature between 200 and 210 ⁰ C and a speed of 200 rpm mixed under protective gas atmosphere and discharged in strand form. The strands are transferred after cooling in a water bath and drying with an air blower in a granulating device by means of rotating blades in a cylindrical granules. The premix thus obtained is after-dried at 70 ^° C. for 3 hours.

Premix Example 2: Thermoplastic copolyester elastomer (TPC) in the form of granules having a Shore hardness of 33 D is dried for 4 hours at 100 ^° C. by means of hot air. On a co-rotating twin-screw extruder with a diameter of 27 mm and an L / D ratio of 40, 85% by weight of TPC and 15% by weight of pyromellitic dianhydride (PMDA) are used at a cylinder temperature between 200 and 210 ^° C. and a speed of 200 rpm mixed under protective gas atmosphere and discharged in strand form. The strands are transferred after cooling in a water bath and drying with an air blower in a granulating device by means of rotating blades in a cylindrical granules. The premix thus obtained is after-dried at 70 ^° C. for 3 hours. Premix comparative example:

Polyester granules (PET) with an intrinsic viscosity of 0.81 dl / g are dried for 8 hrs. At 150 ⁰ C by means of hot air. On the same system as in Example 1 85 wt .-% PET granules and 15 wt .-% pyromellitic anhydride (PMDA) at a cylinder temperature between 240 and 250 ⁰ C and a speed of 200 rpm under a protective gas atmosphere mixed and in strand form discharged. The strands are transferred after cooling in a water bath and drying with an air blower in a granulating device by means of rotating blades in a cylindrical granules. The premix thus obtained is after-dried at 70 ^° C. for 3 hours.

Table 1

Experimental parameters for the preparation of premixes

Example Example Vergleich¬

Premix 1 2 example

recipe

TPC content wt% 85.0 85.0

PET share wt% 85.0

PMDA share weight% 15.0 15.0 15.0

machine parameters

Temperature feed zone ⁰ C 200 200 250

Temperature mixing zone ⁰ C 210 210 250

Temperature Austra- 0C 205 205 240 gszone

Mass temperature ⁰ C 199 204 238

Mass pressure bar 34 12 12

Anchor flow extruder% 52 33 43

Throughput kg / h 20 20 20 Speed extruder rpm 200 200 200

Abzugsgeschwindigk. m / min 30 30 30

premix

Bulk density g / dl 65.4 59.7 76.5

Foaming Example 1

96.3 wt .-% PET granules as starting material having an intrinsic viscosity of 0.81 dl / g are dried for about 5 hours at 170 ⁰ C with dry air and together with 2.7 wt .-% of the premix of Example 1 ( about 11 hours dried with dry air at 60 ^° C.) and 1.0% of a nucleating agent (30% talc in PET, dried for about 11 hours with dry air at 60 ^° C.) are metered into the first extruder of an extrusion foaming plant with two screw extruders, melted, mixed and foamed with CO ₂ . The melt temperature at the exit from the extrusion die is 248 ° C, the output approx. 290 kg / h, the residence time in the extruder approx. 17 min. There are continuously foam bodies, for example approximately cuboidal cross-section, which are cut to plate-shaped foam bodies. The plate-shaped foam bodies are stacked and welded to one another at the contact surfaces, forming foam blocks. The measured values given in the examples are determined on foam sheets which are separated from the foam blocks transversely to the extrusion direction. The viscosity number of the resulting foam is determined according to ISO 1628/5 and is 164.0 ml / g, which corresponds to an intrinsic viscosity of 1.32 dl / g.

Foaming Example 2

96.3 wt .-% PET granules having an intrinsic viscosity of 0.81 dl / g are dried for about 5 hours at 170 ⁰ C with dry air and together with 2.7 wt .-% of the premix of Example 2 (ca. Dried for 11 hours with dry air at 60 ^° C.) and 1.0% of a nucleating agent (30% talc in PET, dried for about 11 hours with dry air at 60 ^° C.) are metered into the first extruder of an extrusion foaming plant with two screw extruders, melted. zen, mixed and foamed with CO ₂ . The melt temperature at the exit from the extrusion die is 249 ^° C., the output is about 290 kg / h, the residence time in the extruder is about 17 min. The viscosity number of the resulting foam is determined according to ISO 1628/5 and is 165.6 ml / g, which corresponds to an intrinsic viscosity of 1.33 dl / g.

Foaming Example 3

86.7 wt .-% PET granules having an intrinsic viscosity of 0.81 dl / g are dried for about 5 hours at 170 ⁰ C with dry air and together with 2.3 wt .-% of the premix of Example 2 (ca. Dried for 10 hours with dry air at 60 ^° C.), 1.0% of a nucleating agent (30% talc in PET, dried for about 11 hours with dry air at 60 ^° C.) and 10% by weight of a thermoplastic copolyester elastomer (TPC) with a Shore hardness of 33 D (dried for about 12 hours with dry air at 100 ^° C.) is metered into the first extruder of an extrusion foaming plant with two screw extruders, melted, mixed and foamed with CO ₂ . The melt temperature at the exit from the extrusion die is 248 ° C, the output about 270 kg / h, the residence time in the extruder about 18 min. The viscosity number of the resulting foam is determined according to ISO 1628/5 and amounts to 162.2 ml / g, which corresponds to an intrinsic viscosity of 1.30 dl / g.

Foaming Comparative Example

96.3 wt .-% PET granules having an intrinsic viscosity of 0.81 dl / g are dried for about 5 hours at 170 ⁰ C with dry air and together with 2.7 wt .-% of the premix of the comparative example (ca. 11 hours dried with dry air at 60 ^° C.) and 1.0% of a nucleating agent (30% talc in PET, dried for about 11 hours with dry air at 60 ^° C.) are metered into the first extruder of an extrusion foaming plant with two screw extruders, melted, mixed and foamed with CO ₂ . The melt temperature at the outlet from the extrusion tool is 247 ⁰ C. The emissions must be reduced to about 200 kg / h in order to realize the required Offenzelligkeitswert of <8%. The residence time in the extruder thus increases to about 24 minute The viscosity number of the resulting foam according to ISO 1628/5 is lower than in Examples 1 and 2, and thus also the correlating intrinsic viscosity (1.27 dl / g), despite the longer residence time at 157.8 ml / g.

The mechanical properties of the resulting foams are listed in Table 2.

Table 2

Mechanical properties of the foams obtained

Claims

claims

1. Thermoplastic polyester foams of high homogeneity, low open-cell content and high shear fracture strain, containing as modifying agent dianhydrides of tetracarboxylic acids,

characterized in that

the polyester foam contains thermoplastic elastomers.

2. Foam body of polyester according to claim 1, characterized in that the thermoplastic elastomers in amounts of 0.5 to 15 wt .-%, based on the weight of the foam body, are included.

3. foam body made of polyester according to at least one of claims 1 or 2, characterized in that are contained as thermoplastic elastomers in the polyester foam thermoplastic copolyester elastomers.

4. Foam body of polyester according to claim 3, characterized in that the thermoplastic copolyester elastomers in amounts of 0.5 to 15 wt .-%, based on the weight of the foam body, are included.

5. A foamed body of polyester according to at least one of claims 3 or 4, characterized in that the thermoplastic copolyester elastomers contain polyester blocks, wherein the polyester blocks of a diol, preferably from 1, 4-butanediol or 1, 2-ethanediol, and a dicarboxylic acid, preferably from terephthalic acid carrying polyethers bearing hydroxyl end groups and esterified in a condensation reaction.

6. foam body of polyester according to at least one of claims 1 to 5, characterized in that the polyester foam has an open-celledness of less than 8% and in particular less than 4%.

7. A foam body made of polyester according to at least one of claims 1 to 6, characterized in that the polyester foam has a shear fracture elongation of more than 12%, usefully more than 16% and preferably more than 50%.

8. A process for the production of foams of thermoplastic polyesters, with high homogeneity, low open-cell content and high shear fracture strain, containing as modifier dianhydrides of tetracarboxylic acids,

characterized in that

a polyester admixed with a premix of thermoplastic elastomers, preferably thermoplastic copolyester elastomers and dianhydrides of tetracarboxylic acids, and blended to form a foam body containing the thermoplastic elastomers or thermoplastic copolyester elastomers in amounts of from 0.5 to 15% by weight based on the weight of the polyester Foam body is foamed.

9. A process for the production of foam bodies from polyesters according to claim 8, characterized in that the polyester with the premix of thermoplastic copolyester elastomers and dianhydrides of tetracarboxylic acids as components of a reactor or mixer, in particular a single- or twin-screw extruder or a multi-screw extruder or a tandem of two single-screw extruders combined or from a twin and a single-screw extruder, fed and mixed therein

10. means for producing foam bodies from polyesters, with high homogeneity, low open-cell content and high shear fracture elongation, including as modifier dianhydrides of tetracarboxylic acids, characterized in that the agent comprises a premix containing thermoplastic elastomers, preferably thermoplastic copolyester elastomers, in amounts of from 25 to 95% by weight, based on the weight of the composition, and dianhydrides of tetracarboxylic acids in quantities from 5 to 30% by weight, based on the weight of the composition.

11. A composition for producing foam bodies from polyesters according to claim 10, characterized in that the agent is a premix comprising thermoplastic copolyester elastomers in amounts of 50 to 90 wt .-%, suitably from 80 to 90 wt .-%, and dianhydrides of Tetracarboxylic acids in amounts of 10 to 25% by weight, suitably from 10 to 15 wt .-%, based on the weight of the composition

12. A composition for producing foamed polyester body according to at least one of claims 10 or 11, characterized in that the agent is a masterbatch containing 0 to 70%, preferably 1 to 50 wt .-%, each based on the weight of the composition Stabilizers, nucleating agents, flame retardants and / or polyesters, suitably a polyester of the same quality as a starting polyester to be modified.